JPH07319372A - Production of hologram - Google Patents

Abstract

PURPOSE:To easily produce a hologram for reconstructing an arbitrary wave front with high accuracy in a short time by decreasing the calculation quantity on a computer. CONSTITUTION:The distribution of a phase and/or amplitude on the hologram surface for forming the desired reconstruction waveform is first calculated by the computer at the time of producing the hologram for reconstructing the arbitrary wave front. Next, the distribution of the phase and/or amplitude calculated by the computer is applied to a laser beam 1B by a space optical modulation element 3 and thereafter, the magnification of the direction orthogonal with the incident direction of the laser beam 1B in the phase and/or amplitude distribution of the laser beam 1B is reduced and the laser beam is made incident as object light on the photosensitive material 2 for hologram recording by an optical system. The object light and the reference light 1A having a coherent property are made incident on the photosensitive material 2. The desired hologram is thus produced by interference of both.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hologram for reproducing an arbitrary wave front, and particularly, it is possible to easily produce a highly accurate hologram in a short time by reducing the amount of calculation on a computer. The present invention relates to a method for producing a hologram that is made possible.

[0002]

Holograms are generally good media for the purpose of reproducing arbitrary wavefronts. However, a hologram obtained by photographing using normal laser light interference actually requires a subject and the like, and thus the subject and the obtained hologram have their own limitations / limitations.

On the other hand, CGH (Computer Generated Holog)
ram) is a technology that can also produce holograms that cannot be produced by laser light or other interference methods. That is, the computer calculates the complex amplitude distribution on the hologram surface for reproducing the desired wavefront,
If you make something that physically realizes this, CG
H is completed.

By the way, as a method for producing such a CGH, conventionally, a calculated pattern is X-rayed.
There are a method of drawing with a Y plotter or the like and reducing the size of the picture to obtain an appropriate size, or a method of directly drawing a pattern using a device having high resolution.

However, in all of these methods, the amount of calculation in the computer is enormous, and therefore, the processing for a long time is required and the amount of data to be handled is enormous.
In addition, since it is necessary to draw a huge amount of data when manufacturing, it also requires a long processing time.
In particular, it is impossible to produce CGH having a relatively large size.

[0006]

As described above, in the conventional method for producing a hologram for reproducing an arbitrary wavefront, the amount of calculation on the computer is extremely large, and it takes a long time to produce the hologram. Therefore, there is a problem that it is difficult to produce a hologram in a short time.

An object of the present invention is to provide a hologram production method capable of easily producing a hologram for reproducing a highly accurate arbitrary wavefront in a short time while reducing the amount of calculation on a computer. Especially.

[0008]

In order to achieve the above object, in the present invention, in producing a hologram for reproducing an arbitrary wavefront, a hologram for forming a desired reproduced wavefront by a computer is first prepared. The phase and / or amplitude distribution on the surface is calculated, and then the spatial light modulator gives the computer-calculated phase and / or amplitude distribution to the laser light, and then the optical system A reference having a coherence with the object light on the photosensitive material for hologram recording by reducing the magnification in the direction orthogonal to the incident direction of the laser light in the phase and / or amplitude distribution of the light to make it enter the photosensitive material for hologram recording. A desired hologram is produced by the incidence of light and the interference between the two.

Here, in particular, a telecentric system is used as an optical system for reducing the phase and / or amplitude distribution of the laser light. The telecentric system is composed of two lenses arranged between the spatial light modulation element and the photosensitive material, and the lens arranged on the spatial light modulation element side has an image focal position such as a pinhole. I am trying to arrange various spatial filters.

Further, the above-mentioned telecentric system is composed of two lenses arranged between the spatial light modulator and the photosensitive material, and the reference light is transmitted to the photosensitive material via the lens arranged on the photosensitive material side. I am trying to make it incident.

Further, the photosensitive material is moved within the surface of the photosensitive material. Further, a liquid crystal display device is used as the spatial light modulator.

[0012]

Therefore, in the method for producing a hologram of the present invention, the laser light whose phase and / or amplitude is modulated by the spatial light modulator is reduced by an optical system (lens system) such as a telecentric system to be formed on the photosensitive material. Incident on
At the same time, by forming interference fringes by interfering with the reference laser beam that is obliquely incident, the carrier wave can be excluded in the calculation on the computer, so the number of sample points can be small, the calculation amount is extremely small, and it can be done in a short time. Calculations can be performed and the amount of data can be reduced.

Further, in the exposure process using the laser beam, a sufficiently fine hologram can be produced even if a spatial light modulator having a coarse resolution is used, and the amount of data is small, and a hologram of a certain size can be obtained by one exposure. Since it can be produced, a highly accurate hologram can be easily produced in a short time.

In this case, the carrier wave is necessary for separating the reproduction wavefront reproduced by the produced hologram and the illumination light incident for reproduction. And, in general, the carrier wave has a higher spatial frequency than the phase and / or amplitude distribution forming the reproduced wavefront, and thus the carrier wave requires a huge amount of data and high resolution in the hologram. In the present invention using interference by laser light, the carrier wave is replaced with a phase distribution on the photosensitive material, which depends on the incident angle of the reference light.

Therefore, according to the present invention, since it is necessary to process only the phase and / or amplitude distribution of only the reproduced wavefront that requires a relatively coarse resolution, the amount of data is small, the calculation time is short, and the resolution is relatively coarse. Even if the spatial modulation element is used, it is possible to produce a hologram having sufficiently fine interference fringes.

On the other hand, of the two lenses arranged between the spatial light modulator and the photosensitive material, a spatial filter such as a pinhole is provided at the image focal position of the lens arranged on the spatial light modulator side. Arranged, when using a liquid crystal display device or the like in the spatial light modulator, by blocking unnecessary light components due to the cell structure of the spatial light modulator, scattering characteristics, etc., less noise, That is, it is possible to manufacture a hologram having a high SN ratio, high accuracy, and high diffraction efficiency.

A lens having a short focal length can be used by injecting the reference light through a lens arranged on the side of the photosensitive material out of the two lenses arranged between the spatial light modulator and the photosensitive material. As a result, the range of selection for the lens system of the device is increased, and the device can be downsized.

Further, the photosensitive material is placed on a stage such as an XY stage, and the stage is controlled to move in the plane of the photosensitive material to perform exposure while appropriately changing the exposure position on the photosensitive material. Therefore, it becomes easy to manufacture a hologram having a relatively large size.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. (First Embodiment) FIG. 1 is a schematic diagram showing a configuration example of a CGH producing apparatus for realizing a hologram producing method according to a first embodiment of the present invention.

In this embodiment, a hologram is produced by the following method. That is, as shown in FIG.
First, a computer (not shown) calculates the distribution of phase and / or amplitude on the hologram surface for forming a desired reproduction wavefront.

Next, the laser beam emitted from a laser light source (not shown) is divided into two, and one of the laser beams 1A is made incident on the photosensitive material 2 for hologram recording as a reference beam.

Further, the other laser beam 1B is made incident on a spatial light modulator 3 such as a liquid crystal display device, and the spatial light modulator 3 modulates the phase and / or the amplitude of the laser beam 1B.

At this time, the spatial light modulator 3 is adapted to perform phase and / or amplitude modulation for forming a desired reproduced wavefront calculated by a computer, and this reproduced wavefront does not include any consideration regarding the carrier. Absent.

After that, the optical system 4 reduces the magnification of the phase and / or amplitude distribution of the laser beam 1B in the direction orthogonal to the incident direction of the laser beam 1B, so that the laser beam on the photosensitive material 2 is used as object light. It is incident on the same position as 1A.

Here, as the optical system 4 for reducing the phase and / or amplitude distribution of the laser beam 1B, for example, a telecentric system can be used. As the telecentric system, the spatial light modulator 3 and the photosensitive material 2 are used. It is composed of two lenses 41 and 42 arranged between the two.

As a result, the photosensitive material 2 has a reference light (laser light 1B) which is coherent with the object light (laser light 1B).
A) is incident on the photosensitive material 2 to produce a desired hologram by the interference between the two, that is, an interference fringe of a desired reproduction wavefront (laser light 1B) and a carrier wave provided by the reference light (laser light 1A). To record as a hologram.

The hologram recorded in this manner is subjected to processing such as development, if necessary, and then
A desired reproduction wavefront can be obtained by entering appropriate illumination light.

As the reproduced wavefront in this embodiment, any wavefront can be applied. For example, the display of a three-dimensional object that does not actually exist, or even if it actually exists, it cannot be obtained by a normal method, an optical element, etc. Realized easily.

In FIG. 1, the object light (laser light 1
B), the behavior of the light flux of the reference light (laser light 1A) is shown by a solid line, the imaging relationship of the surface of the spatial light modulator by the lens system is shown by a dotted line, and the wavefront of the light is shown by a broken line.

Next, in the hologram manufacturing method according to the present embodiment as described above, the laser light 1B whose phase and / or amplitude is modulated by the spatial light modulator 3 is used.
Is reduced by an optical system (lens system) 4 such as a telecentric system and is incident on the photosensitive material 2, and at the same time, interference is generated with a reference laser beam 1A that is obliquely incident, thereby forming an interference fringe. Since the carrier wave can be excluded in the above calculation, the number of sample points is small, the calculation amount is extremely small, the calculation can be performed in a short time, and the data amount can be reduced.

In this case, the carrier wave is necessary for separating the reproduction wavefront reproduced by the produced hologram from the illumination light incident for reproduction. And, in general, the carrier wave has a higher spatial frequency than the phase and / or amplitude distribution forming the reproduced wavefront, and thus the carrier wave requires a huge amount of data and high resolution in the hologram. In this embodiment using interference by laser light, the carrier wave is replaced with a phase distribution on the photosensitive material, which depends on the incident angle of the reference light.

For example, when the incident angle of the reference light on the surface of the photosensitive material 2 is θr, the carrier wave pitch (= reciprocal of frequency) d
Is expressed by the following equation. d = (sin θr) ⁻¹ · λ where λ is the wavelength of the laser beam during hologram recording.

On the other hand, in the exposure process using a laser beam, a hologram consisting of sufficiently fine interference fringes can be produced even if the spatial light modulator 3 having a coarse resolution is used, and the amount of data is small, so that exposure can be performed to a certain extent. Since a hologram having a size can be produced, a highly accurate hologram can be easily produced in a short time.

As described above, in the present embodiment, since only the phase and / or amplitude distribution of only the reproduced wavefront that requires a relatively coarse resolution need be processed, the amount of data is small, the calculation time is short, and the relatively coarse. Even if a spatial modulation element having a resolution is used, a hologram having sufficiently fine interference fringes can be produced.

FIG. 2 is a schematic diagram showing the reproduction of the hologram created according to this embodiment. As described above, in the present embodiment, when producing a hologram, the computer first calculates the distribution of the phase and / or the amplitude on the hologram surface for forming the desired reproduced wavefront, and then the space is calculated. The light modulation element 3 gives the distribution of the phase and / or the amplitude calculated by the computer to the laser light 1B as the object light, and thereafter, the two laser light arranged between the spatial light modulation element 3 and the photosensitive material 2 are provided. A telecentric system, which is an optical system composed of the lenses 41 and 42, reduces the magnification in the direction orthogonal to the incident direction of the laser beam 1B in the phase and / or amplitude distribution of the laser beam 1B and reduces the magnification as object light for hologram recording. Reference light (laser light 1A) which is made incident on the photosensitive material 2 and has coherence with the object light (laser light 1B).
And a desired hologram is produced by the interference between the two.

Therefore, since the carrier wave can be excluded from the calculation on the computer, the number of sample points is small, the calculation amount is extremely small, the calculation can be performed in a short time, and the data amount can be reduced. .

Further, in the exposure process using the laser beam, a hologram composed of sufficiently fine interference fringes can be produced even if the spatial light modulator 3 having a coarse resolution is used, and the amount of data is small, so that the exposure can be performed to a certain extent by one exposure. Since a hologram having a size can be produced, a highly accurate hologram can be easily produced in a short time.

As described above, since it is necessary to process only the phase and / or amplitude distribution of only the reproduced wavefront that requires a relatively coarse resolution, the amount of data is small, the calculation time is short, and the spatial modulator having a relatively coarse resolution is used. Even if 3 is used, a sufficiently fine hologram can be produced.

(Second Embodiment) FIG. 3 shows a C for realizing a hologram manufacturing method according to a second embodiment of the present invention.
FIG. 2 is a schematic diagram showing a configuration example of a GH creation device, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Only different parts will be described here.

That is, in the present embodiment, as shown in FIG. 3, of the two lenses 41 and 42 arranged between the spatial light modulator 3 and the photosensitive material 2 which constitute the telecentric system in FIG. The spatial filter 5 is arranged at the image focus position of the lens 41 arranged on the side of the spatial light modulator 3 so that a hologram is produced.

In the hologram manufacturing method according to the present embodiment as described above, the spatial light modulator 3 is provided by disposing the spatial filter 5 at the image focus position of the lens 41.
Spatial light modulator 3 when a liquid crystal display device or the like is used for
By cutting off unnecessary light components due to the cell structure and scattering characteristics of the
It is possible to manufacture a hologram having a high N ratio, high accuracy, and high diffraction efficiency.

As described above, in the hologram manufacturing method according to this embodiment, the same effects as in the case of the first embodiment described above can be obtained, and in addition to this, unnecessary light can be obtained. Since it is possible to cut off the ingredients of
It is possible to manufacture a hologram with little noise, that is, a high SN ratio, with high accuracy and high diffraction efficiency.

(Third Embodiment) FIG. 4 shows C for realizing a method for producing a hologram according to a third embodiment of the present invention.
FIG. 2 is a schematic diagram showing a configuration example of a GH creation device, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Only different parts will be described here.

That is, in the present embodiment, as shown in FIG. 4, of the two lenses 41 and 42 arranged between the spatial light modulator 3 and the photosensitive material 2 which constitute the telecentric system in FIG. The reference light (laser light 1A) is incident on the photosensitive material 2 through the lens 42 arranged on the photosensitive material 2 side to form a hologram.

In the method for producing a hologram according to the present embodiment as described above, the degree of freedom in arrangement is increased, for example, the distance between the lens system and the photosensitive material 2 can be reduced.
The range of selection for the lens system of the device is increased, and the device can be downsized.

As described above, in the hologram manufacturing method according to the present embodiment, the same effects as in the case of the first embodiment described above can be obtained, and in addition to this, the spatial light modulator is also provided. Since the reference light (laser light 1A) is incident on the photosensitive material 2 through the lens 42 arranged on the photosensitive material 2 side among the two lenses 41 and 42 arranged between the photosensitive material 2 and the photosensitive material 2, As a result, the range of selection for the lens system of the device is increased, and the device can be downsized.

Further, the lens 4 arranged on the side of the photosensitive material 2
Even if the focal length of 2 is short, the reference light (laser light 1
It is possible to make A) incident on the photosensitive material 2 at a desired angle.

As a result, even when the reduction ratio is high, it is possible to easily deal with it. In addition, the degree of freedom of the optical system 4 can be increased. The present invention is not limited to the above embodiments, but can be implemented in the same manner as described below.

In each of the above embodiments, the photosensitive material 2 was replaced with X-.
It is possible to perform exposure while appropriately changing the exposure position on the photosensitive material 2 by placing it on a stage such as a Y stage, and controlling this stage to move it within the surface of the photosensitive material 2. It is also extremely easy to produce the hologram.

[0050]

As described above, according to the present invention, when a hologram for reproducing an arbitrary wavefront is produced, first, a phase on the hologram surface for forming a desired reproduced wavefront is calculated by a computer. And / or an amplitude distribution is calculated, and then the spatial light modulator imparts a computer-calculated phase and / or amplitude distribution to the laser light, after which the optical system causes the phase and / or amplitude of the laser light to be calculated. Alternatively, the magnification in the direction orthogonal to the incident direction of the laser light in the amplitude distribution is reduced and made to enter the photosensitive material for hologram recording as the object light, and the reference light having coherence with the object light is made to enter the photosensitive material. Since the desired hologram is created by the interference between the two, the amount of calculation on the computer is reduced, and a highly accurate arbitrary wavefront is reproduced in a short time. Hologram manufacturing method capable of easily producing a hologram of the order can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a CGH creating device for realizing a hologram manufacturing method according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing how a hologram created in the same example is reproduced.

FIG. 3 is a schematic diagram showing a configuration example of a CGH creating device for realizing a hologram manufacturing method according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration example of a CGH creating device for realizing a hologram manufacturing method according to a third embodiment of the present invention.

[Explanation of symbols]

1A ... Laser light (reference light), 1B ... Laser light (object light), 2 ... Photosensitive material for hologram recording, 3 ... Spatial light modulator, 4 ... Optical system, 41, 42 ... Lens, 5 ... Spatial filter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuyuki Okada 5-6-4-303 Konakadai, Inage-ku, Chiba-shi, Chiba (72) Inventor Toshiki Toda 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Stock In-house (72) Inventor Torou Iwata 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.

Claims (6)

[Claims] 1. A method for producing a hologram for reproducing an arbitrary wavefront, which comprises first calculating a distribution of phase and / or amplitude on a hologram surface for forming a desired reproduced wavefront, Next, the spatial light modulation element gives the laser beam a distribution of the phase and / or amplitude calculated by the computer, and thereafter, an optical system is used to provide the laser beam with a phase and / or amplitude distribution of the phase and / or amplitude of the laser beam. The magnification in the direction orthogonal to the incident direction is reduced and made to enter the photosensitive material for hologram recording as object light, and the reference light having a coherence with the object light is made incident on the photosensitive material to cause a desired interference due to interference between the two. A method for producing a hologram, characterized in that a hologram is produced. 2. The hologram manufacturing method according to claim 1, wherein a telecentric system is used as an optical system for reducing the phase and / or amplitude distribution of the laser light. 3. The telecentric system is composed of two lenses arranged between the spatial light modulator and a photosensitive material, and a space is provided at an image focal point of the lens arranged on the spatial light modulator side. The method for producing a hologram according to claim 2, wherein a filter is arranged. 4. The telecentric system is composed of two lenses arranged between the spatial light modulator and a photosensitive material, and the reference light is passed through a lens arranged on the photosensitive material side. The hologram manufacturing method according to claim 1, wherein the hologram is made incident on the photosensitive material. 5. The method of producing a hologram according to claim 1, wherein the photosensitive material is moved within a surface of the photosensitive material. 6. A liquid crystal display device is used as the spatial light modulator.
A method for producing a hologram according to claim 5.